ASTM A773/A773M-96
(Test Method)Standard Test Method for dc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs
Standard Test Method for dc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs
SCOPE
1.1 This test method provides dc hysteresigraph procedures ( B-H loop methods) for the determination of basic magnetic properties of materials in the form of ring, toroidal, link, double-lapped Epstein cores, or other standard shapes that may be cut, stamped, machined, or ground from cast, compacted, sintered, forged, or rolled materials. It includes tests for normal induction and hysteresis taken under conditions of continuous sweep magnetization. Rate of sweep may be varied, either manually or automatically at different portions of the curves during tracing. Total elapsed time for tracing a hysteresis loop is commonly 10 to 120 s per loop.
1.2 The values stated in either customary (cgs-emu and inch-pound) units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the systems may result in nonconformance with this test method.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: A 773/A 773M – 96 An American National Standard
Standard Test Method for
dc Magnetic Properties of Materials Using Ring and
Permeameter Procedures with dc Electronic
Hysteresigraphs
This standard is issued under the fixed designation A 773/A 773M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope A 596 Test Method for Direct-Current Magnetic Properties
of Materials Using the Ballistic Method and Ring Speci-
1.1 This test method provides dc hysteresigraph procedures
mens
(B-H loop methods) for the determination of basic magnetic
2.2 Other:
properties of materials in the form of ring, toroidal, link,
IEC Publication 404-4: Magnetic Materials—Part 4: Meth-
double-lapped Epstein cores, or other standard shapes that may
ods of Measurement of dc Magnetic Properties of Iron and
be cut, stamped, machined, or ground from cast, compacted,
Steel (1995)
sintered, forged, or rolled materials. It includes tests for normal
induction and hysteresis taken under conditions of continuous
3. Summary of Test Method
sweep magnetization. Rate of sweep may be varied, either
3.1 As in making most magnetic measurements, a specimen
manually or automatically at different portions of the curves
is wound with an exciting winding (the primary) and a search
during tracing. Total elapsed time for tracing a hysteresis loop
coil (the secondary) for measuring the change in flux. When an
is commonly 10 to 120 s per loop.
exciting current, I, is applied to the primary winding, a
1.2 The values stated in either customary (cgs-emu and
magnetic field, H, is produced in the coil, and this in turn
inch-pound) units or SI units are to be regarded separately as
produces magnetic flux f in the specimen. In uniform speci-
standard. Within the text, the SI units are shown in brackets.
mens that do not contain air gaps, such as ring samples, all of
The values stated in each system are not exact equivalents;
the exciting current is used to magnetize the specimen, and H
therefore, each system shall be used independently of the other.
is proportional to I in accordance with the following equation:
Combining values from the systems may result in nonconfor-
H 5 KI
mance with this test method.
(1)
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
where:
responsibility of the user of this standard to establish appro-
H 5 magnetic field strength, Oe [A/m],
priate safety and health practices and determine the applica-
I 5 current in the exciting coil A, and
bility of regulatory limitations prior to use.
K 5 constant determined by the number of primary turns
the magnetic path length of the specimen and system
2. Referenced Documents
of units.
2.1 ASTM Standards:
3.1.1 The magnetic flux may be determined by integration
A 34 Practice for Sampling and Procurement Testing of
of the instantaneous electromotive force that is induced in the
Magnetic Materials
secondary coil when the flux is increased or decreased by a
A 341 Test Method for Direct-Current Magnetic Properties
varying H. The instantaneous voltage, e, is equal to:
of Materials Using dc Permeameters and the Ballistic Test
df
Methods
e52NK (2)
dt
A 343 Test Method for Alternating-Current Magnetic Prop-
or
erties of Materials at Power Frequencies Using the
Wattmeter-Ammeter-Voltmeter Method and 25-cm Epstein
2 f5 edt
*
Frame
K N
where:
dt 5 time differential,
This test method is under the jurisdiction of ASTM Committee A-6 on
Magnetic Properties and is the direct responsibility of Subcommittee A06.01 on Test
Methods.
Current edition approved Dec. 10, 1996. Published March 1997. Originally
published as A 773 – 80. Last previous edition A 773 – 91. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 03.04. Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
A 773/A 773M
that is induced in an H-coil (or Chattock potentiometer) or
N 5 number of turns, and
−8
from the signal developed by a Hall probe which is placed near
K 5 10 for cgs-emu system, or K 5 1 for SI system.
1 1
the specimen. When using an H-coil, the determination of H is
accomplished with an H integrator in exactly the same manner
The flux f can be obtained if |Mi edt can be determined. This
as that used to determine flux with the B integrator described in
can be accomplished by several means, as described in ASTM
3.1. When using a Hall sensor, the H values are determined
STP 526. (1) The most common method utilizes an electronic
from the voltage output which is proportional to H. In some
integrator consisting of a high-gain dc amplifier with resistive-
cases, the H versus I relationship may be sufficiently linear
capacitive feedback. The relationship to |Mi edt is:
from 0 to the coercive field strength ( H ) of the material under
c
E 5 edt (3)
test. In such cases it is acceptable to determine the second
*
RC
quadrant of the hysteresis loop by determining H from the
where:
value of I in the exciting winding.
E 5 output voltage, V,
4. Significance and Use
R 5 input resistance of the integrator in the secondary
circuit, V, and
4.1 Hysteresigraph testing permits more rapid and efficient
C 5 the feedback capacitance, F.
collection of dc hysteresis (B-H loop) data as compared to the
By combining the two equations:
point by point ballistic Test Methods A 341 and A 596. The
ERC fNK accuracy and precision of testing is comparable to the ballistic
f5 or E 5 (4)
K N RC
methods. Hysteresigraphs are particularly desirable for testing
of semi-hard and hard magnetic materials where either the
If the voltage, E, is applied to the Y axis of an X-Y recorder,
entire second quadrant (demagnetization curve) or entire hys-
the Y deflection of the pen is proportional to the flux, f.
teresis loop is of primary concern.
3.1.2 Measurements of magnetic field strength and flux by
4.2 Provided the test specimen is representative of the bulk
the hysteresigraph method is illustrated in the block diagram of
sample or lot, this test method is well suited for design,
Fig. 1. The system consists of a magnetizing power source, an
specification acceptance, service evaluation and research and
exciting current controller, an electronic flux integrator, and a
development.
data recorder. As exciting current is applied to the coil, a
voltage proportional to I is produced across the shunt resistor
5. Interferences
which is connected in series with the primary coil. This voltage
5.1 Test methods using suitable ring-type specimens are the
determines the value of H.
preferred methods for determining the basic magnetic proper-
3.1.3 In the testing of hard magnetic materials, or soft
ties of a material. However, this test method has several
magnetic materials in the form of wire, bars or rods, it is
important requirements. Unless adequate inside diameter to
usually necessary to use a permeameter. This is shown in the
outside diameter ratios are maintained in the test specimens,
block diagram of Fig. 2. When using permeameters, the value
the magnetic field strength will be excessively nonuniform
of H in the gap is generally not proportional to I that flows
throughout the test material and the measured parameters
through the exciting coil of the yoke. In these cases, the value
cannot be represented as material properties. The basic quality
of H is determined by integration of the electromotive force
of materials having directional sensitive properties cannot be
tested satisfactorily with punched rings or laminations. With
them it is necessary to use Epstein specimens cut with their
The boldface numbers in parentheses refer to the list of references at the end of
lengths in the direction of specific interest or use long
this test method.
FIG. 1 Block Diagram of Ring Test Apparatus
A 773/A 773M
FIG. 2 Block Diagram of Permeator Test Apparatus
TABLE 1 Permeameters Recommended for Use With
link-shaped or spirally wound core test specimens whose long
Hysteresigraphs
dimensions are similarly oriented. The acceptable minimum
NOTE 1—Other permeameters may be suitable for use with dc hyster-
width of strip used in such test specimens is also sensitive to
esigraphs where appropriate modifications are made. Refer to Test Method
the material under test. At present, it is believed the silicon
A 341 for other permeameters.
steels should have a strip width of at least 3 cm [30 mm].
Unless ring specimens are large, it is difficult to provide
Permeameter Magnetic Field Strength Range H Measurement
sufficient magnetizing turns or current-carrying capacity to
Device
Oe kA/m
reach high magnetic field strengths. In general, magnetic
Babbit (2,3) 40/100 3.2/8 current, H-coil
materials tend to have nonuniform properties throughout the
Fahy Simplex (4,5,6) 0.1/300 0.008/24 H-coil
body of the test specimens; for this reason, uniformly distrib-
Fahy Simplex Super 100/2500 8/200 H-coil
H Adapter (6)
uted test windings and uniform specimen cross-sectional area
IEC Type A 12/2500 1/200 H-coil, Hall probe
are highly desirable to average nonuniform behavior to a
IEC Type B 12/620 1/50 H-coil
tolerable degree. Isthmus (6, 7) 100/20 000 + 8/1600 + H-coil, Hall probe
5.2 When conducting permeameter tests on bars, rods, and
other appropriate specimens, this test method covers a range of
magnetic field strengths from about 0.05 Oe [4 A/m] up to
section, they may have undetected nonuniform magnetic prop-
about 20 000 Oe [1600 kA/m] or more, depending on the
specimen geometry and the particular permeameter that is erties radially or axially along the specimen length adjacent to
the H or B coils. Some permeameters may also introduce
employed. In general, the lower limit of magnetic field strength
is determined by the area-turns of the H coil (or the sensitivity clamping strains into the test specimen. For these reasons test
results obtained on a test specimen with one type of permeame-
of the Hall probe if it is used), the sensitivity of the integrator,
and the sensitivities of the measuring and recording compo- ter may not compare closely with those obtained on the same
nents. The upper limitation in magnetic field strength is specimen from another type permeameter, and both may differ
determined by the type of permeameter appropriate for the from more precise testing methods.
specimen, the power supply, and the heat generated in the yoke 5.2.2 The limitation in the B measurement by this test
windings. Recommendations of the useful range of magnetic method is determined by the number of turns on the specimen,
field strength for the various permeameters are shown in Table the cross-sectional area, the permeability, and the sensitivities
1. Other types may be used with appropriate precautions. of the B integrator and X-Y recorder. In general, normal
5.2.1 In general, permeameters do not maintain a uniform induction and hysteresis data may be determined from a flux
−5
magnetic field in either the axial or radial directions around the linkage corresponding to 1000 Maxwell-turns [10 Weber
test specimen. The field gradients in both of these directions turns] to an upper induction that corresponds to the intrinsic
will differ in the various permeameters. Also the H-sensing and saturation for most materials.
B-sensing coils of the different permeameters are not identical 5.2.3 Some permeameters utilize compensation coils and
in area, in turns, or in length or identically located. Although require continual adjustment of the current flowing through
test specimens are prepared to have uniform physical cross these coils. This may not be compatible with commercially
A 773/A 773M
available hysteresigraphs and can be a source of significant to outside diameter ratio not less than 0.82). When the test
error. specimen has smaller ratios than the above requirements, the
5.2.4 The magnetic test results, particularly for high perme- test data should not be represented as material properties but
ability alloys, may not exactly agree with test results obtained should be called core properties because of nonuniform flux
by the ballistic methods, Test Methods A 341 and A 596. This distribution.
is due to the influence of eddy currents and the different nature 7.4 When link, oval-shaped, or rectangular test-specimen
of the magnetizing waveform between hysteresigraph and forms are used, the requirements of 7.3 apply to the end or
ballistic testing. corner sections where flux crowding occurs. When straight-
sided test specimens are very long relative to the length of the
6. Apparatus
corner or end sections, they are suitable for basic material
6.1 The apparatus shall consist of as many of the compo-
properties evaluation with relatively unoriented materials,
nents described in 6.2 through 6.6 as required to perform the
provided the uncertainty in determination of true-path (effec-
tests.
tive) length is less than 1 % of the total path length. When this
6.1.1 All apparatus used in this test method shall be cali-
uncertainty in path length (shortest or longest relative to the
brated against known standards to ensure the accuracy limits
mean-path length) exceeds 1 %, the test values should be
given below.
reported as core properties and not basic material properties.
6.2 Balance or Scales:
7.5 The test specimen may be constructed of solid, lami-
6.2.1 The balance or scales used to weigh the test specimen
nated, or strip materials and in any of the shapes described in
shall be capable of weighing to an accuracy of 0.2 %.
1.1.
6.2.2 The micrometer or dimensional measuring scales used 7.6 Test-specimen cores made from strip may be laminated,
to determine specimen dimensions for calculation of cross-
machined, spirally wound, or Epstein specimens (the method
sectional area shall be capable of measuring to an accuracy of of selection for Epstein specimens is described in Annex A3 of
at least 0.1 %.
Test Method A 343). When the material is to be tested half
6.3 Magnetizing Power Source—The power source may transverse and half longitudinal, the material shall be cut into
range from simple batteries to sophisticated regulated, low-
Epstein strips or square laminations of adequate dimensional
ripple, protected, programmable types. It shall have sufficient ratio.
capacity to produce the maximum currents required for mag-
7.7 Test specimens used for basic material evaluation shall
netiza
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